Remove obsolete hpack version from stack-8.0.yaml
Remove obsolete hpack version from stack-8.0.yaml

sjakobi/stack,Fuuzetsu/stack,deech/stack,anton-dessiatov/stack,AndrewRademacher/stack,Blaisorblade/stack,MichielDerhaeg/stack,juhp/stack,mrkkrp/stack,MichielDerhaeg/stack,martin-kolinek/stack,Heather/stack,Blaisorblade/stack,AndrewRademacher/stack,Heather/stack,martin-kolinek/stack,AndreasPK/stack,mrkkrp/stack,AndreasPK/stack,juhp/stack,Fuuzetsu/stack,sjakobi/stack,deech/stack,anton-dessiatov/stack